At present, filters used in internal combustion engines suffer from a multitude of deficiencies, the most important being: their low filtering capacity and low yield, since the filtering element is quickly saturated with sediment and dirt contained in the element being filtered. On the other hand, the large amount of the element subject to filtering which leaks through the exit connection of filters without having contact with the filtering element, thus causing filtration deficiency.
Filters used in heavy duty internal combustion engines are generally placed in a hollow cylinder that has a cap on the upper part, an entrance conduit for the element to be filtered and a conduit placed on the lower part that allows the element for filtration to exit once it has passed through the filter.
Now, therefore, when the element for filtration penetrates inside the above-mentioned hollow cylinder, which for brevity of the term we will hereinafter call "filter box", and is submitted to a determined pressure and will therefore try to exit by the point of least resistance, that is, the element subject to filtration will have basically two paths to follow:
The first will be by passing through the filter until reaching the central, hollow part of it, to exit via the exit conduit of the above-mentioned filter box, thus performing perfect filtration.
The second path whereby the element to be filtered can exit will be without passing through the filter, since logically this represents greater resistance; this exit path which the element subject to filtration will have will be by the point where the filter makes contact with the exit connection of the filter box.
Having established the foregoing, at present, at the point where the filter connects with the exit conduit of the filter box there is no packing that makes a perfect seal, which results in leaks and consequently, deficient filtration.
The above problem is worsened inasmuch as filter boxes do not have an exit conduit with a standard diameter, but on the contrary, these exit conduits have different diameters and what is more, some internal combustion engine filter boxes simply are manufactured without a guide in the exit conduit.
As regards the filtering medium used in filters for heavy duty internal combustion engines, they must meet certain physical and chemical characteristics in order to operate adequately and overcome the often found problem with water that is introduced into the lubricating oil. The problem of water in the lubricating oil, for example that used in locomotives, is very common and causes serious problems if an appropriate lubricating oil filter is not used in the engine of the locomotive. The result of using an inappropriate filter is that the water softens and swells the filter, the filter becomes weakened and the edge of the bottom of the fold extrudes inside the central filter pipe, thus causing blockage of the line or at least a reduction in the flow rate, that is, a high pressure drop. In order to test the filter materials to determine if they will be appropriate for use in locomotive engines, a water extrusion resistance test has been formulated with the aim of testing it in the filter medium. In the test, first the flow-resistance of the filter paper to the lubricating oil is tested at a certain temperature and flow rate. Then, the paper is tested as to flow resistance against a water in oil emulsion (generally around 1% water in an oil emulsion), at the same temperature and flow rate. A ratio of the respective pressures measured, that is, the pressure .times.gpm of emulsion/pressure to .times.gpm of lubricating oil is indicative of an adequate form of the filter means. The industry generally considers that when it is greater than 1.1, it is inadequate for application in locomotive lubricating oil filters.
Because the problem of water often appears in locomotive lubricating oil, until now the industry has adopted the use of a paper filter with a covering on one side of cotton down fibers. The filter used is essentially that described in the U.S. Pat. No. 3,116,245 issued to Robert W. McNabb and Howard L. Dahlstrom. The use of cotton down fibers results in a filter means that exhibits good resistance to the extrusion of water and good filtering characteristics. The problem with using cotton as a source, however, is the cyclical variance in supply. Even though cotton is available, the price is prohibitive, that is, $1200US/ton, in comparison with other wood pulps such as "Kraft" wood pulps, whose average price is $300US/ton. The use of Kraft pulp in the filter means for application in filtering locomotive lubricating oil is inadequate; however, since the filter means may exhibit poor resistance to water extrusion. In order to provide a filter means that replaces at least to a substantial degree, the cotton that is generally used, it would benefit the industry if the filter means functioned adequately as a locomotive lubricating oil filter, that is, if it exhibited adequate resistance to water extrusion.